Bone cements for anchoring joints and repairing other bone defects consist of a synthetic material which as a rule is based on methylmethacrylate or related substances, in some cases with the addition of further esters of acrylic acid or methacrylic acid. Such bone cements are described e.g. in DE 196 41 775 A1. Frequently, a combination of benzoyl peroxide and dimethyl-p-toluidine is used as a catalyst in the liquid monomer, which is pointed out as a disadvantage in DE 196 35 205. Bone cements are usually prepared by mixing two components. One component contains the liquid monomer, the other is made up of a powdery polymer provided in the form of spherical particles having a diameter of approx. 100 μm.
X-ray contrast media are added for achieving the X-ray opacity required for control purposes. Known X-ray contrast media are BaSO4 and ZrO2, which are added in amounts ranging between 7 and 30%.
Currently, a great variety of bone cements are used, they do, however, still have disadvantages.
A general problem consists in that heat is exothermally released during polymerization. However, the bone cells which are in contact with said bone cements are damaged if the temperature rises above 50° C. The actual thermal stress put on body cells within the zone of contact with the polymerizing bone cement can only be predicted very inaccurately. It depends on the thickness of the cement layer applied, on the thermal conductivity via the prosthesis components as well as on the bone itself. Laboratory tests have shown that maximum temperatures of up to 110° C. may occur during the polymerization of commercially available cements under certain conditions, causing burns as a consequence. Improvements seem to be necessary in this respect.
Another problem of the bone cements known so far is that residual monomer which is always contained therein as well as other additives, e.g. the stabilizer hydroquinone (toxicity class 3) and the accelerator N,N-dimethyl-p-toluidine (toxicity class 2), may dissolve out, thus causing damage.
Furthermore, the shrinkage resulting from polymerization may have a disadvantageous effect which may, in the end, lead to a loosening of the prosthesis.